LAPACK  3.4.0
LAPACK: Linear Algebra PACKage
Functions/Subroutines
dlarz.f File Reference

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Functions/Subroutines

subroutine DLARZ (SIDE, M, N, L, V, INCV, TAU, C, LDC, WORK)
 DLARZ

Function/Subroutine Documentation

subroutine DLARZ ( CHARACTER  SIDE,
INTEGER  M,
INTEGER  N,
INTEGER  L,
DOUBLE PRECISION, dimension( * )  V,
INTEGER  INCV,
DOUBLE PRECISION  TAU,
DOUBLE PRECISION, dimension( ldc, * )  C,
INTEGER  LDC,
DOUBLE PRECISION, dimension( * )  WORK 
)

DLARZ

Download DLARZ + dependencies [TGZ] [ZIP] [TXT]
Purpose: 

 DLARZ applies a real elementary reflector H to a real M-by-N
 matrix C, from either the left or the right. H is represented in the
 form

       H = I - tau * v * v**T

 where tau is a real scalar and v is a real vector.

 If tau = 0, then H is taken to be the unit matrix.


 H is a product of k elementary reflectors as returned by DTZRZF.
Parameters:
[in]SIDE
          SIDE is CHARACTER*1
          = 'L': form  H * C
          = 'R': form  C * H
[in]M
          M is INTEGER
          The number of rows of the matrix C.
[in]N
          N is INTEGER
          The number of columns of the matrix C.
[in]L
          L is INTEGER
          The number of entries of the vector V containing
          the meaningful part of the Householder vectors.
          If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0.
[in]V
          V is DOUBLE PRECISION array, dimension (1+(L-1)*abs(INCV))
          The vector v in the representation of H as returned by
          DTZRZF. V is not used if TAU = 0.
[in]INCV
          INCV is INTEGER
          The increment between elements of v. INCV <> 0.
[in]TAU
          TAU is DOUBLE PRECISION
          The value tau in the representation of H.
[in,out]C
          C is DOUBLE PRECISION array, dimension (LDC,N)
          On entry, the M-by-N matrix C.
          On exit, C is overwritten by the matrix H * C if SIDE = 'L',
          or C * H if SIDE = 'R'.
[in]LDC
          LDC is INTEGER
          The leading dimension of the array C. LDC >= max(1,M).
[out]WORK
          WORK is DOUBLE PRECISION array, dimension
                         (N) if SIDE = 'L'
                      or (M) if SIDE = 'R'
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Contributors:
A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA
Further Details:

Definition at line 146 of file dlarz.f.

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